This seems true in North Korean media, though I can't say what's taught in their schools. As I understand, 한자 (Hanja) was no longer in use in 북한 (DPRK, aka North Korea) by the end of the Korean War, and upheld this way as the regime wants to maintain a monolithic culture among its people.
To substantiate this somewhat, it is even strongly frowned upon (if not outright forbidden) to call their language 한국어 (Korean, in South Korea), the word 조선말 (Chosun-mal) being the correct term, derived from the historic kingdom of Korea, Chosun. (This is not due to animosity against South Korea, but on the contrary, because North Koreans believe that all Koreans are one people and destined to reunify, as was the case during the five centuries of the Chosun kingdom.) There is a strong sense of national pride in their language when there.
Source: Traveled from 평양 (Pyongyang) to 원산 (Wonsan) and 함흥 (Hamhung), browsed several bookstores, was exposed to much media (posters, pamphlets, billboards, newspapers, etc.), and spoke with many local North Koreans.